Refrigerator Troubleshooting Diagram

Archive for the ‘Room Air Conditioners’ Category

Room Air Conditioners Automatic Expansion Valves

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Automatic expansion valves are used on some room air conditioners instead of the capillary tubes to control the flow of refrigerant into the evaporator. These valves are set to maintain a normal suction pressure. They are factory adjusted and sealed, and no field adjustment is required. A small bleed port in the valve permits pressure equalization from the high to low side on shutdown. A small liquidline strainer is located in the liquid line ahead of the expansion valve.

Written by sam

February 8th, 2011 at 6:59 am

Room Air Conditioners Refrigerant Leaks

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Whenever a shortage of refrigerant is suspected, this condition can be confirmed by identifying the source of leakage. A leak-test operation can be performed with a halide leak detector. The end of the exploring hose is passed around areas where a refrigerant leak is suspected. The air drawn into the hose passes through a copper reactor plate and through a small flame. If any refrigerant is contained in this air, the color of the flame turns slightly green. If a considerable quantity of refrigerant is leaking, the flame turns purple. When the location of leak has been determined, it is sometimes difficult to pinpoint the exact leak location. Soapsuds can be used to pinpoint the exact source of leak.

Written by sam

February 8th, 2011 at 6:58 am

Room Air Conditioners Compressor Amperage

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With normal evaporator loading and average outdoor temperatures, if proper cooling is being accomplished, the compressor motor will draw the approximate amperage shown on the unit nameplate. If a unit is drawing considerably below compressor nameplate amperage, the refrigerant system may not be producing proper cooling, assuming that there is a normal flow of air over the evaporator and that the evaporator loading is not abnormally low.

Written by sam

February 8th, 2011 at 6:57 am

Room Air Conditioners Evaporator Temperature

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Under average operating conditions of outdoor and indoor temperatures, all evaporator return bends should be cold and at the same approximate temperature. On most models, this check can be easily made by removing the front grille. If the first evaporator passes are iced over, or if there is a noticeable temperature increase of the return bends of the last several passes, it could be an indication of either restriction or loss of refrigerant. It must be remembered, however, that with higher outdoor temperatures, the very last evaporator pass will not have as much refrigerant to effect cooling as it would have at lower temperatures. Therefore, it will be at a slightly higher temperature if the outside temperature is high.

Frequently, servicemen check the dry-bulb temperature drop across the evaporator to determine if the unit is cooling satisfactorily. The temperature drop across the evaporator is not the same on all units. Higher outdoor dry-bulb temperatures and high inside relative humidity tend to reduce the dry-bulb temperature drop across the evaporator. On most units with an outdoor temperature between 80◦F and 90◦F and with an indoor relative humidity between 40 and 50 percent, the temperature drop across the evaporator should be between 17◦F and 20◦F. Where proper evaporator air flow is maintained, a 20◦F dry-bulb temperature drop would normally indicate satisfactory cooling. When the room air relative humidity is considerably higher than 50 percent, a smaller dry-bulb temperature drop across the evaporator will be obtained. When the relative humidity is considerably below 40 percent, a higher temperature will result. It is, therefore, important that room air relative humidity be checked and considered when checking air temperature drop across the evaporator as a check for proper cooling.

Written by sam

February 8th, 2011 at 6:56 am

Room Air Conditioners Refrigerant-System Service

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When a unit operates but does not have its normal cooling capacity, the refrigerant system should be checked. Check for some obvious symptom (such as partial icing of the evaporator, an abnormally warm suction line, or other unusual condition) that could indicate a loss of refrigerant or a restricted capillary tube.

The refrigerant system of most room air-conditioning units is a sealed-type circuit. Should trouble develop that requires opening the refrigerant circuit, the usual caution and requirements for repair of a capillary-tube–type system are necessary. This requires equipment for evacuating and leak testing, as well as a means of accurate refrigerant charging. Observe all appropriate safety precautions specific to the refrigerant.

Written by sam

February 8th, 2011 at 6:55 am

Room Air Conditioners Compressor and Motor

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The compressor motor is a capacitor-type, split-phase motor that has two windings. The starting winding has the capacitor in series with it to give great starting torque, with the winding composed of a smaller-size wire than the running winding. By using a capillary tube method of refrigeration, the starting load is normally rather low. At the start, the running winding is energized, drawing a larger starting current, which causes the relay to close the starting winding contacts, energizing the starting winding almost immediately.

As the motor comes up to speed, the current value drops. At about 65 percent of full speed, the current drops low enough for the starting relay to open the circuit to the starting winding and the full load is then carried by the running winding. If the load is too heavy, the current draw will be large and the overload protective device will open and stop the motor until the overload protection cools, when it will again attempt to start the motor.

To check the continuity of the compressor motor winding, disconnect the three motor leads C, S, and R (Figure 5-28), making sure the entire unit is unplugged from the source of electrical supply. The ohmmeter should show continuity between any two of the three terminals, with a larger resistance between terminals C and S than between C and R. If the ohmmeter shows no resistance on any of the tests, an open winding is indicated.

While making the preceding test, you should test the compressor motor for grounding. This is done by putting the ohmmeter on its highest scale and touching one lead to the compressor housing and the other to each of the motor terminals, one at a time. If the winding is not grounded, the ohmmeter should read full scale (or the maximum resistance) in ohms.

It must be remembered that faults other than motor trouble may be the cause of compressor failure or of a motor drawing high current. Some of the compressor failure causes are a stuck compressor, high head pressure, low voltage, or a plugged capillary tube.

Written by sam

February 8th, 2011 at 6:53 am

Dismantling Window Air Conditioners

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This section lists the procedure and steps necessary to dismantle window air conditioners. The procedure can be used in its entirety or in part, according to the service required. The procedure covers only those parts of the unit that can be serviced in the field and is not a complete disassembly. By presenting a dismantling procedure, it is possible to eliminate repetition of certain steps common to many service operations. Keep in mind that individual manufacturers may recommend a slightly different procedure. In all instances, follow the instructions of the manufacturer when dismantling an air conditioner. When reassembling the unit, the steps should be reversed.

To dismantle the air conditioner, proceed as follows:

1. Disconnect the air conditioner from the source of electric supply, and remove the cabinet.
2. Remove the electric control boxes. Remove the screws that secure each box to the partition. Remove the control-box covers, and disconnect the motor leads. Remove the control box assemblies from the unit.
3. Remove the fan motor and fans. Loosen both fans, and remove them from the shaft. Remove the access panel that fits down over the cooling-unit fan shaft. Loosen and remove the motor cradle supports at each end of the motor. Lift the motor up and out.

Written by sam

February 8th, 2011 at 3:25 am

Room Air Conditioners Service Operations

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Room-air-conditioner servicing is similar to refrigerator servicing. An air conditioner is a refrigerant system that removes heat from a room. (In a refrigerator, the heat is removed from the food.) An evaporator is employed to remove the heat, and a condenser is used to liquefy the refrigerant. Air movement over the evaporator and condenser surface is accomplished by a fan. Hot air usually contains a greater percentage of moisture than colder air. When the evaporator fan moves hot humid air over the cold surface of the evaporator, a quantity of the moisture in the air will condense (form water droplets) in addition to the air itself being cooled. In this manner, the relative humidity of the recirculated air is also reduced. The condensate water is drained into the condenser section, where it is dissipated.

Servicemen who have a good knowledge of refrigeration combined with the understanding that an air conditioner removes heat and humidity from a room by the process of refrigeration will be able to competently service air conditioners. Since most portable air conditioning units of present design contain compressors of the hermetic or sealed type, the only parts that can be serviced in the field are the relay, control switch, fan, fan motor, starting and running capacitors, air filters, and cabinet parts. The refrigerating system (consisting of the cooling unit, condensers, compressors, and connecting lines) generally cannot be serviced in the field.

Written by sam

February 8th, 2011 at 3:23 am

Room Air Conditioners Unit Control Switch

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The unit control switch may be located on top of the cabinet or on one of the sides, depending upon the particular design. The control switch is usually of the knob- or rotary-control dial type and normally has four positions, marked OFF, FAN, COOL, and EXHAUST. The damper controls are usually marked SHUT, VENT, and OPEN. To provide cooling, the switch dial is turned to the COOL position, and the damper dial to SHUT or VENT depending on whether or not outside air is desired.

To operate the unit as a ventilator, the switch dial is turned to FAN and the damper dial is turned as far open as desired. In the OPEN position, the unit passes in 100 percent of outside air. To exhaust room air, the switch is turned to the EXHAUST position, and the damper dial is turned to the VENT position. When a thermostat is installed for automatic cooling, the compressor and fans will cycle according to dial requirements.

Written by sam

February 8th, 2011 at 3:21 am

Room Air Conditioners Thermostats

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The thermostat (or temperature control) stops and starts the compressor in response to room temperature requirements. Each thermostat has a charged power element containing either a volatile liquid or an active vapor charge. The temperature-sensitive part of this element (thermostat feeler bulb) is located in the return air stream. As the return air temperature rises, the pressure of the liquid or vapor inside the bulb increases, which closes the electrical contacts and starts the compressor. As the return air temperature drops, the reduced temperature of the feeler bulb causes the contacts to open and stops the compressor.

The advent of transistors and the semiconductor chips or integrated circuits has produced a more accurate method of monitoring and adjusting temperatures within a system. The microprocessor makes use of the semiconductor and chip’s abilities to compare temperatures and to program on and off cycles, as well as monitor the duration of each cycle. This leads to more accurate temperature control.

Figure 5-25 shows a microprocessor-based thermostat. As you can see from the front of the control panel, you can adjust the program to do many things and, in the process, save energy, whether it is operating the furnace for heat or the air-conditioning unit for cooling. These units usually come with a battery so that the memory can retain whatever is programmed into it. The battery is also a backup for the clock so that the program is retained even if the line power is interrupted.

Written by sam

February 8th, 2011 at 3:20 am

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